Best Invasive

The Chinese mitten crab is a highly invasive freshwater crustacean native to East Asia, distinguished by its furry claws and its destructive impact on European river ecosystems.

Caulerpa racemosa is a pantropical green alga that invaded the Mediterranean from the 1990s onward, outcompeting native seagrasses and algae across vast seafloor areas.

Red alga native to Australia and the Southern Hemisphere that established itself as an invasive species on European Atlantic coastlines by the early 20th century, now widely naturalized.

Codium fragile is a spongy green alga native to the Pacific that has invaded Atlantic and Mediterranean coasts, widely known as 'dead man's fingers' for its branching thalli.

A predatory snail native to the southeastern USA, introduced to Hawaii and Pacific islands as biocontrol in the 1950s–70s but responsible for driving dozens of endemic snail species to extinction.

A large East African land snail reaching up to 20 cm, listed among the world's 100 worst invasive species and federally restricted in the USA.

The Asian Paddle Crab is a large crustacean native to the coastal waters of the western Pacific, distinguished by its paddle-shaped hind legs used for rapid swimming.

Orange Hawkweed (Hieracium aurantiacum) is a European native introduced to North America that is considered an invasive weed in many regions, recognizable by its vivid orange-red flower heads.

A freshwater gastropod native to South America that became a major invasive agricultural pest in rice-growing regions across Asia and Hawaii during the late 20th century.

The green shore crab is a globally invasive predator native to the northeastern Atlantic Ocean that disrupts ecosystems in North America and Australia.

Dictyosphaeria cavernosa is a tropical green alga forming hollow, bubble-like colonies on coral reefs, used as a bioindicator of eutrophication and reef degradation.

A grasshopper native to North Africa and the Middle East that has established invasive populations in the Canary Islands, where it displaces native species.

A freshwater gastropod native to Africa and Asia that has become invasive on multiple continents, valued in aquariums for burrowing through substrate and improving aeration.

Native to eastern North America and invasive in European waters since the late 19th century via oyster imports, this species is a sequential hermaphrodite forming stacked chains.

Opuntia dillenii is a prickly pear native to the Americas, now naturalized across Africa, Asia, and the Mediterranean, where it is considered a significant invasive weed.

The Chinese shore crab is a small crustacean native to the coastal waters and rocky intertidal zones of East Asia, often studied for its complex mating and territorial behaviors.

The White-fingered Mud Crab is a small, highly adaptable crustacean native to the eastern United States, recognized by its pale-tipped claws and global invasive spread in brackish waters.

An invasive red alga native to Asia that spread to European Atlantic coasts by the late 20th century, where it establishes dense mats and outcompetes native algal species.

The Asian swamp eel (Monopterus albus) is an air-breathing freshwater fish native to South and East Asia, capable of surviving drought by burrowing into mud and respiring air.

A freshwater gastropod native to South America and among the world's largest freshwater snails, with shells capable of exceeding 15 cm in diameter.

The Flat Rock Crab is a marine crustacean known for its distinctly flattened body, which allows it to hide in narrow coastal rock crevices around the world.

The Devil Crab is a marine crustacean known for its heavily calcified, spiky exoskeleton, inhabiting coral rubble and rocky substrates throughout the Indo-Pacific region.

The cactus moth (Cactoblastis cactorum) is a South American species famously introduced to Australia in the 1920s to biologically control invasive prickly pear cacti.

The Chinese Mystery Snail is a large freshwater gastropod native to East Asia that has become a prominent invasive species in North American waterways.

A Mediterranean snail that became a serious agricultural pest in Australia after introduction, notorious for mass aestivation in dense clusters on crop stems.

Native to New Zealand, the Jenkins' Spire Shell is a tiny aquatic snail that has become a highly successful invasive species across North America and Europe.

A small North American land snail introduced worldwide, notable as an intermediate host for Angiostrongylus cantonensis, a rat lungworm capable of infecting humans.

Red alga native to Japan that spread to European Atlantic coastlines by the late 19th century, distinguished by prominent hook-like lateral branchlets and now considered naturalized in Europe.

The Freshwater Trumpet Snail is a burrowing gastropod found across Southeast Asia and Australia, characterized by its elongated, conical shell.